power: supply: cpcap-battery: Check voltage before orderly_poweroff

We can get the low voltage interrupt trigger sometimes way too early,
maybe because of CPU load spikes. This causes orderly_poweroff() be
called too easily.

Let's check the voltage before orderly_poweroff in case it was not
yet a permanent condition. We will be getting more interrupts anyways
if the condition persists.

Let's also show the measured voltages for low battery and battery
empty warnings since we have them.

Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>